Radio amplifying system



July 8, 1930. G. w. PICKARD RADIO AMPLIFYING SYSTEM 4 Sheets-Sheet 2 Filed May '7, 1923 ATTORNEY July 8, 1930. e. w. PICKARD I RADIO AMPLIFYING SYSTEM Filed ma 7, 1925 4 Sheets-Sheet 5 IN V EN TOR 1930. G. w. FICKARD 1,770,143

RADIO AMPLIFYI NG SYSTEM r 1 Patented July 8,1930 f UN E ATES PATENT. OFFICE]:

' GREENLEAF WHITTIER PICKARI), or nnwrouonurua, MASSACHUSETTS, ASSIGNOB .thermionic tubes TO WIRELESS SPECIALTY APPARATUS CORPORATION OF NEW YORK.

COMPANY, OF BOSTON, MASSACHUSETTS, A

RADIO AMPLIFYING SYSTEM Application .filed May 7,

This invention relates to improvements in amplifying radio receiving systems.

. An object of the invention is to obtain maximum amplification with minimum number of thermionic tubes.

The invention resides in the methods and apparatus described below and shown in the drawings, of which q Figures 1 and 2 show a preferred embodiment, Fig. 1 being generally schematic to show the route taken by the currents through the system, and Fig. 2 being a. complete dia gram of the arrangement of the circuits and apparatus, all the individual pieces of apparatus being well-known in theart, i. e., the (audions), batteries, the amplifier transformers, filter transformers, and the aerials, oscillator, rheostat, condensers, and telephones, all of which. may be of any of the well-known types and of values suitable for use with the particular tubes and frequencies involved in any particular design of receiving set' employing the invention;

Fig. 3 is a general schematic drawing of a modified form which lacks certain features of the form of Figs. 1 and'2 which figures, however, illustrate the arrangement of circuits and apparatus for the embodiment of Fi 3.

Figs. 1 and 5 show another modification which employs less tubes, although a form found by me to constitute a practical embodiment of the invention; Fig. 4: being schematic (as Fig. 1),and Fig. 5 being a complete working diagram (as Fig. 2).

Fig. 6 is a schematic two radio frequency reflexes, i. e., three radio frequency amplifications by the same audion tubes (and an audio frequency reflex), and illustrating the fact that the number of radiofrequency reflexes is limited only by the,

upper limit of received radio frequency or input from the aerial.

The invention is particularly useful in receiving radio communications having wavelengths of the order of a hundred meters more or less, that is, frequencies of the order of from, say several millions offcycles per less. 3 'As shown in Fig. 1,:there may be four am- (14c) more or even less, an

drawing showing 19%. Serial No. 637,063, second down to one hundred thousand or plifier tubes oscillator tube 5 and a detector tube 6 (or the functions of tubes Band 6 may be executed by a singletube as, wellknown) ,fil- I ters F .and F constructed to pass only one band of frequencies each; and a telephone or other receiver R, with a small wave-.collector' or aerial A.

In operation, the radio frequency currents first, upon reception, are amplified by tubes 1& prior to any detection (rectification); also, prior to any actual detection, currents from oscillator 5 are added to the input or received radio frequency currents, the. ur-

rents from tube 5 being ofv such frequency as will form, radio frequency beats with said input. currents, of lower frequency than the latter, all as indicated in Fig. 1 by way of example. (Thenumerals on Fig. 1 represent frequencies.) As iswell known in het;

erodyne or beats practice, the oscillator frequency may have any one of a large number of values different from the input frequency,

such as approximately the input frequency J plus or minus the desired beat frequency, or half the input frequency plus or minus the desired beat frequency, or, say, one-third the input. frequency plus or minus the desired beat frequency, etc. The above route through the tube-system is indicated by line X, i. e., the part of the system traversed by the input radio frequency.

In detector tube 6 are rectified input and local oscillator which are at radio frequency and which contain the radio frequency as a beat. From tube 6 along routeY pass the rectified radio frequency beats; all other frequencies ,(including as yet unampli-fie-d audio frequencies which may pass through the other filter F being blocked by filter F from passage beyond detector 6 in this route Y. k

. Route Y takes theradio frequency beat current through amplifying tubes 1 4: back to detector 6, which now rectifies it, producing the audio frequency current originally present in the input X as modulated atthe the mixed frequencies, both of through" amplifier tubes distanttransmitten-for route Z to filter F (Filter F prevents a passage through route Z of radio beats which properly pass through diagram of Fig. 2 1s in general-the same as in schematic'Fig. 1, as. abovedescribed.

and plates of tubes 1+6. The complete circuits are shown in Fig. 2,' in lieu of the single lines or routes of Fig. 1" which there repre sent thetwosides 'ofeach circuit; -Thefilal mentsfare co'nnectedby buses as usual to the Abattery (BA) via filament rheostat H. Plate battery BB-is shown as usual. Tl1e amplifier transformers between the tubes are i illustrated by I their accessories densers.

I inclusive.

cillations including, by-pass con Those'transformers which are in route X of Fig. 1 are marked inFig. 2 X XQX X those in route Y are marked inclusive; and those in route Z Z-,Z Conductors in Fig.2 which are traversed by thecurrents in routes X, Yand Z of Fig. 1 are likewise'marked in. Fig, 2. Detector tube G is shown as provided with the'usual grid-leak GL and grid condenser Oscillator tube is shown as provided with the usual'gfrequency determining elements F D, feed-backFB andmixer coil M',"the

latter in inductive relation to amplifier transformerX whereby the locally gen'erated-osare supplied as in Fig.1 to the input current just before rectification by detector tube'6;although,as stated in connection with Fig. 1 this supply may be to the input currents at any stage of their amplification or before they have been amplified at-all, becausethere is-not need of amplifying the locally generated oscillations because they may be generated with anydesired amplitude.

' In Figs. 1-2 there are successively three amplifications by'the same tubes, first at a high order of radio frequency (that of input X), second at a lower order of radio frequency (radio frequency beats), and third, at audio frequency. a @In Fig. 3 is shown in the manner of Fig. 1 amodification which lacks audiofrequency. route Z of Figs. 1-2 through the amplifying tubes. From tubeljinFig. 3, the current previously first amplified by tubes 1+4, rectified by tube 6*and again amplified at reduced radio beat frequencybytubes 14l,

is rectified to audio frequency and led'at Z directlyto the indicator R, without, as in Figs. 1+2, being first further amplified (at audio. frequency) by tubes 1+4. Otherwise the system of Fig. 3 is the same as audion detector 6 of Figs.

' In F 1g. 2 are shown}the-filaments,grids V In Figs. 4 and 5 is shown asystem like that of Figs. 1-2 in having radio and audio reflexes or routes X and Y through the ampli- I fier and the detector; but a solid rectifier or crystal detector 6 is shown in lieu of the 13, and only one amplifier" (a tube 1) is shown in lieu of the four amplifier tubes1- 1 of Figs. l3. The os- 'cillator 5 maybe a tube as 111'F1gs. 1-3. In Fl 's. l-5 the oscillator 5 is shown as hav1n its current mixedwith the'inp'ut prior to any amplificatlon of the 1nput,.1. e., the oscillator is connected to the input circuit in advance of amplifier 1, instead of being-connected to the detector 6 asinFigs. 13. the usual conventions wlth In general, the operation of Figs. l5 is like that above-disclosed of Fig. .1. YVit-h any form of the pr sent inventioma small aerial maybe used, or a minimum number of tubes, or both.

The detailsof Fig. 5 (the complete diagram for the scheme of- Fig. 4) are. similar to the 'details'of 2 (the diagram of the scheme 'ofFig. 1). In Fig. 5, where the ,oscillator 5is coupled to the input prior to any amplification, the mixing coil Mnaay be, as shown, "the secondary of atransformer of which the primary is the entire loop aerial A itself, coil L being mounted to berotatable with looplaerial A... Of 'CQUISG gTOLlIIClGCl antennae may be used in lieu of the loop aerial in all cases. I

In the diagrannFig; 5, transformer-X passes the amplified currents of route from the platecircuit of tube lto detector 6. Also transformer Y passes the amplifiedY currents from the plate circuit of tube 1 to de tector 6. A grid battery GB is inserted in thegrid-filament circuit of the tube.

'In Fig. 5 oscillator o supplies to input X and detector-6 a radio frequency current of plus or minus 360 meters. as indicated in Fig- 5, i. e.,; such a radio frequency as will produce (with input X) a radio frequency beat. This beat is rectified by crystalVdetectort and is passed through filter F which is constructed to pass only the resultant beat frequency (5,000 meters indicated in Fig. 5) to routeY (Figs. 4

'. and This beat frequency inroute Y then is amplified by tube 1 and passed again to detectorfi where it'is again rectified. The

product of this second rectification is audio frequency current passing in the Z route.

This audio frequenoy then'is amplified by frequency beingv sufficiently high (as in present-day broadcasting with short waves), i. e., 100 meters (3,000,000 cycles per second) there are two radio reflexes through the two amplifying tubes 1 and 2, and the detector tube 6 (i. e., three successive radio frequency amplifications by the same tubes, each amplification being followed bya rectification by tube 6 and a consequent reduction of degree of frequency; the third or last rectification resultingin audio frequency Z). This is one more radio frequency amplification by'the same tubes than in Figs. 1-5.

Before the first of the two reflexes, (second radio frequency amplification), oscillator tube 5 supplies frequency U at the value noted on the drawing (i. e., the input'frequency in aerial A plus or minus the" desired higher radio beatfrequency of 200,000). The rectified mixture of'input and oscillator fre-' quencies passes from rectifier tube 6 via filter F and route X to the two amplifying tubes 12 for the second radio frequency amplification. For the second reflex (third radio frequency amplification) oscillator 5 supplies frequency V at the Value noted on the draw ing (i. e., the first beat frequency of 200,000

plus or minus the desired higher radio beat frequency of 30,000). Route Y via filter F then takes the rectified product of such amplification (at the lower beat frequency) to tubes 12, the third radio frequency for amplification. (Such lower beat frequency is the result of the mixture of the first or higher beat.

frequency with the V frequency of oscillator Route Z via filter F finally takes the rectified product of such amplification, in the form of audio frequency, totubes .1-1 .for

final or audio frequency amplification, whence such currents pass to indicator R for observation. i

The advantages of the invention include the following.

The amplificationof the radio frequency input prior to detection and the mixture of the locally generated oscillations with the input prior to detection cause greatlyincreased amplifying eificiency because, as the operation of detection obeys an input-voltage square-law, the detector output of beat current is thereby enormously increased by such amplification in combination with such heterodyning prior to detection. By this means is greatly extended the practical'limits heretofore existing to amplification by heterodyning and even super-heterodyning. To the end of obtaining maximum amplification with minimum tubes, the above result in enhanced greatly by the described reflexing once (two radio frequency amplifications by thesame tubes) twice (three radio frequency amplifications by the same tubes), or' even more times, ofthe beats at successively lower degrees-of radio frequency, all of wh ch am-- plification is finally enhanced by the rectification of the final product of the last amplification of the radio frequency beats and the finalrefiexing of such audio frequency product before observation 'by the receiving phones. Greatly exceeding any a1nplification heretofore possible is that obtained'by v the use of the sametubes in this invention for amplifying at radio frequency several successive i3111'lGS,'1 e., at successively lower radio beat frequencies, by successive heterodyning at radio frequency. As appears hereinbefore, t 1s the reduction from higher to lower radlo. frequency by the beats operation whlch per mits reamplification at radio frequency by the same tubes. The beats operation, therefore, serves as a means which permits successlve amplifications at radio frequency by the same I that is necessary being the supply-from oscil- .lator 5 in any of the figures hereof, of an ad rlitioiial radio frequencyof such value as will produce an audio frequency beat note with' the last or lowest radio frequency beat in the system, such value being for ex. mple, in the,

case of Fig. 6, 80,000 cyclesplus or minus the frequency of the desired audible beat note such as 500 to 1,000 cycles per second,'corre'- sponding with the musical note for tele graphic dots and dashes as in the ordinary heterodyne of the prior art. a

Herein, as in all systems of high 'amplifi cation, it is essential to avoid, so far as possible, all feed-backs which would produce undesirable oscillations. No set rule can be laid down for the exact disposition of the apparatus and leads; but when such undesirable oscillations are found to occur, they may be stopped by changingthepoling'or direction of connection in circuit of'the windings of the transformers and filters. Also, the various parts of the apparatus, especially the transformers, may be changed in relative lo-' cation until such oscillations thereby are stopped. Also, as a substantial portion of the undesirable feed-backs occur between leads connecting various elements of the apparatus, the relative positions of such leads may bealtered as a means for stopping such oscillations, Again, such undesirable oscillations may be stopped by counteracting the displacement currents from plate to grid (WllICll are a prolific cause of such oscillaextremely useful Without any such refiexing, in which case the product of the first rectification of amplifiedand heter'odynediinput is led-direct to receiving telephone R, in any of the figures, The refiexing of the" radio beat "frequency all figures) ,is especially advane vtageous,-however, not merely inextent of amplification, but in thefreedomof distort on ascomparedwith audio frequency reflex'ing, due, to the fact that suchbeats, being at radio frequency and coveringonly a narrow frequency band, can be re-aniplified, and repeatedly, amplified, by the same tubes, at successively reduced radio beat 'frequencies,'.

Without resulting distortion such as occurs With the reflexing of {audio frequencies covconstructor is advised to obtain desiredhigher amplification 1n the use of the invention ployed overa fractionofthe succession of amin 7 b? q 7 v V advantageously if not to excess; and at ering a wideflband. In this connection, the

rather-by reflexing "(re-amplification) of radio frequency Vbeats- 1(Figs. 1-5)" and by frequency repeated refiexing of the radio beats (Fig; 6) than by audio frequency reflexalthough thelatter also may be used times audiofrequency refiexing maybe em- -plifyirigjtubes if not over all of those "employed for radio frequency amplification;

further specific illustration of a preferred form ofthe inventlon, constructed along the lines of the drawings, 18 one employing four amplifying tubes as in Fig. 1') all-being con-j,

nected to amplifyithe radio frequency input, (asiniF 1g. 1), but tubes numbers 2-4111- clusivebeing constructed for reflex amplification of radio frequency beats, and tubes numbers13-l inclusive being connected for reflex amplification v ofaudio frequency For I have found that, as the frequency is made lower in successive reflex stages, the stabili ty of thetrain of amplifier tubes is decreased,

so that it becomes advantageous in maintaining stability of the tubes in use at av given stage, to reduce their numberas in the above illustration. y ii I claims e V 1.f The method of radio amplification by thermionic amplifying means, which consists,

prior to detectioinin amplifying received radlo frequency currents at theirfradio frequency by such means andmlrlng w th said radofrequencycurrents a locally generated frequency causingthe production of radio frequency beats,'then rectifying such radio frequency beats; and prior to observation,

passing the rectified product through more or less of the same said amahf 1l ml11S.

2. The methodiof radio amplification b I thermionic amplifying means, which consists,

prior to detection, in amplifying received rad o frequencycurrents at their radio frequency by suchmeans and mixing With said radio frequency currentsa locally. generated frequency caus ng the production of rad o beats also irior to detectionfrequency beats; then rectifying such radio frequencybeats; then prior to'a second rectification, passing said rectified product through more or less of the same said amplifyingmeans and mi:

product through more or less of the same said amplifying means; rectifying said amplified radio frequency currents to audio frequency; and, prior to observation, passingsaid audio frequency currents through more or less of the same said-amplifying means.

The methodof radio amplification by thermionic amplifying means, which consists,

prior to detection, in, amplifying received radio frequency currents at their radio fre quency by such means and mixing th m with locally generated heterodyning frequency subsequently changing to audio frequency and'passing the audio frequency currents through more or less of the same said amplifyii'igmeansr Themethod of radio amplification by thermionic amplifying means, which consists prior to detection in amplifying received radio frequency currents at their radio frequency by such means and mixing with them a locally generated heterodyning frequency causing the production of beats; filtering out all currents save those of such beats; fore observation, passing such beats through more 7' or less of the same said amplifying means.

j 6. A thermionic tube amplifier, which comprises 1 thermionic amplifying means con nected to amplify the received' currents at radio frequencyrmeansfor mixing heterodyning currents with the received currents prior to rectification; means 'forrectifying the resulting beats; means for filtering out all currents savethose of the beats; and connections from the filtering means to more or less of the same said thermionicamplify ng means to cause amplification of the beats. 7 A thermlomc tube amplifier, wliiclicolnprises thermionic amplifying means connected to amplify the received currents at radio frequency; means for mixing heterodyniing-currents with the received currents prior to rectification; means for rectifying the with said rectified product a locally-generated frequency causthen prior to a and, be-

IOU

beats;means for passing the resulting beats through more or less of said thermionic amplifying means and through said rectifying means;.means for passing the resulting currents one or more additional times through more or less of said thermionic amplifying means; and a plurality of filtering means each located in one of the paths from the rectifying means to the thermionic amplifying means.

8. The method of amplifying radio fre quency currents which consists in passing them thru a thermionic amplifying system and reducing them to a lower degree of radio frequency; passing such reduced radio frequency currents thru a greater or less extent of the same said amplifying system and reducing the frequency to audio frequency; and passing such'audio frequency currents thru a greater or less extent of the same said amplifying system.

9. A thermionic tube amplifier which comprises thermionic amplifying means connected to amplify received radio currents at their received radiofrequency; means for reducing the frequency to a lower degree of radio frequency; means for passing the lower radio frequency currents thru a greater or less extent of the same said amplifying means and means for filtering currents of other fre= quencies from the path of the'lower radio frequency currents to said amplifying means.

10. The method of amplifying radio frequency currents, which consists in passing them at radio frequency thrua thermionic amplifying system and also forming the radio frequency currents into radio frequency beats, both prior to detection; subsequently changing the radio frequency beats to audio fre quency currents; passing the audio frequency currents thru a greater or lessextent of the same said amplifying system; and finally observing the amplified audio frequency currents.

11. The method of amplifying radio frequency currents which consists in passing them thru a thermionic amplifying system and reducing the frequency to a lower degree of radio frequency of amplified current; passing the reduced radio frequency amplifie current thru a greater or less extent of the same said amplifying system while blocking currents of other frequencies from their path from frequency change to such amplification; subsequently changing the frequency to audio frequency; and passing said audio frequency currents thru a greater or less extent of the same said amplifying system while blocking currents of other frequencies from the path from frequency change to such amplification.

12. The method of amplifying radio frequency currents, which consists in passing them at their input radio frequency thru a thermionic amplifying system; heterodyning r them at the same frequency and rectifying the resulting radio frequency beats, produ cing a 1 lower degree of radio frequency currents; and

less extent of a path between rectification and amplification.

13. The method of amplifying radio, frequency currents, which consists in passing them thru a thermionic amplifying system at their radio frequency and in heterodyningthem at said frequency, both prior to detection; then passing them thru a detector tube subsequently passing the currents of reduced frequency thru a greater or less extent of the same said amplifying system; and finally passing-the currents thru the same said detector tube and observing the resulting currents. V

14 The method of amplifying radio frequency currents, which consists in passing them at radio frequency amplifying system and in heterodyning them at the same frequency, both prior to detection; and then passing them thru a detector tube, reducing them to a lowerdegree of radio frequency then passing the currents of reduced radio frequency thru a greater or less extent of the same said amplifying system;

thru a thermionic V to its input, each connection being arranged to pass a different frequency, and means as-- sociated with said amplifier to change the frequency of the energy each time it passes 1 through the amplifier, each change corresponding to the frequency passed by a different one of said re-entrant connections. GREENLEAF WHITTIER PIGKARD. 

